Signal Intensity In T2-weighted Images Research Articles

Segmentation of nasopharyngeal carcinoma (NPC) lesions in MR images

An accurate and reproducible method to delineate tumor margins from uninvolved tissues is of vital importance in guiding radiation therapy (RT). In nasopharyngeal carcinoma (NPC), tumor margin may be difficult to identify in magnetic resonance (MR) images, making the task of optimizing RT treatment more difficult. Our aim in this study is to develop a semiautomatic image segmentation method for NPC that requires minimal human intervention and is capable of delineating tumor margins with good accuracy and reproducibility. The segmentation algorithm includes 5 stages: masking, Bayesian probability calculation, smoothing, thresholding and seed growing, and finally dilation and overlaying of results with different thresholds. The algorithm is based on information obtained from the contrast enhancement ratio of T1-weighted images and signal intensity of T2-weighted images. The algorithm is initiated by the selection of a valid anatomical seed point within the tumor by the user. The algorithm was evaluated on MR images from 7 NPC patients and was compared against the radiologist's reference outline. The algorithm was successfully implemented on all 7 subjects. With a threshold of 1, the average percent match is 78.5 +/- 3.86 (standard deviation) %, and the correspondence ratio is 66.5 +/- 7%. The segmentation algorithm presented here may be useful for diagnosing NPC and may guide RT treatment planning. Further improvement will be desirable to improve the accuracy and versatility of the method.

Quantitative measurement of regional signal intensity changes of high grade gliomas following radiotherapy using T1-weighted contrast enhanced MRI imaging

Quantitative measurement of regional signal intensity changes of high grade gliomas following radiotherapy using T1-weighted contrast enhanced MRI imaging

Longitudinal myelitis associated with systemic lupus erythematosus: clinical features and magnetic resonance imaging of six cases

Myelopathy is a rare central nervous system (CNS) complication associated with systemic lupus erythematosus (SLE). Acute transverse myelitis (ATM) is the most frequent form of SLE-related myelopathy. Magnetic resonance imaging (MRI) typically shows increased signal intensity in T2-weighted images and cord swelling. In the present paper, we describe six cases of SLE-related myelopathy with multiple increased signals in the T2-weighted images involving continuous levels of the cervical and thoracic spinal cord, a distinctive feature recently named 'longitudinal myelitis'. The clinical and laboratory findings are similar to those presented by ATM patients, including paraparesis, sensory level and sphincter disturbances. Four patients had positive antiphospholipid antibodies (aPL) suggesting that this could be a characteristic of longitudinal myelitis. Treatment in all cases included high doses of corticosteroids and immunosuppressive agents (intravenous (i.v.) cyclophosphamide). Anticoagulation therapy was given to one patient and two others received low doses of aspirin. The outcome was mainly unfavorable with slow improvement in only one case, no improvement in two and relapse of the myelopathy in the remaining three. In conclusion, longitudinal myelitis is an unusual form of SLE-related myelopathy, it might be associated with aPL and it has a poor prognosis.

Diagnostic imaging of giant cell tumors

Although classified as benign neoplasms, giant cell tumors are locally aggressive with a high recurrence rate of 30-50%. The histological appearance include osteoclast-like, multinucleated giant cells and round to spindle-shaped mono-nuclear stromal cells. These neoplasms predominately affect adults in the third and forth decades of life (70-80%). Giant cell tumors predominately arise in long tubular bones (75-95%) with the majority occurring around the knee (50%). The next most common site being the distal radius (10%). The epicenter of giant cell tumors is in the epiphysis. The radiographic signs of giant cell tumors are a geographical radiolucency with no internal mineralization, a thinning of the cortex, eccentric in the epiphysis of long bones. MRI signs of giant cell tumors are high signal intensity in T2-weighted images, high contrast media enhancement, fluid levels, signs according to haemorrhage and haemosiderin deposition. CT shows the expanded and thinned cortex. Plain radiographs remain the mainstay of diagnosis of giant cell tumors. MRI and CT are important for staging and therefore for surgical planning.

Hemiparkinsonism associated with the unilateral striatal necrosis: a case report

We report a patient with hemiparkinsonism associated with unilateral striatal necrosis of the contralateral side. The patient was an 18-year-old woman who had a two-month-history of difficulty in executing skilled movements with her right upper extremity. Neurological examination revealed that she had cogwheel rigidity and bradykinesia in her right upper and lower extremities. MRI revealed a well-delineated low signal intensity in T1-weighted and high signal intensity in T2-weighted images in the region of the putamen on the left side. Her laboratory data were unremarkable and mitochondrial gene mutation studies revealed no abnormality. It is extremely rare to encounter a case of parkinsonism associated with unilateral striatal necrosis.

Head and neck tumors: imaging recurrent tumor and post-therapeutic changes with CT and MRI

Objective: To evaluate criteria for detection of tumor recurrence and post-treatment changes in patients with head and neck malignancies in computed tomography (CT) and magnetic resonance imaging (MRI). Methods and materials: Thirty-nine patients with head and neck carcinoma receiving radiochemotherapy were examined before, during and after therapy with MRI. Changes in signal intensity were correlated to histology or clinical course. Three hundred and thirty-one patients with head and neck malignancies were examined with CT after therapy. CT diagnoses were correlated with histology or clinical course. Results: Main criteria for recurrent/residual tumor in MRI was infiltrative mass with high signal intensity in T2-weighted images and enhancement after Gd-DTPA in T1-weighted images. Radiation-induced changes led to false positive diagnosis in 46% in the interval up to 3 months after therapy and in 58% in the interval 3–6 months after therapy. The combination of a circumscribed, infiltrative mass with contrast enhancement in CT had a sensitivity of 86% and a specificity of 80%. Conclusion: CT could accurately demonstrate postoperative changes and tumor recurrence. MRI had advantages in differentiation of tumor and scar, but edema after radiation therapy can spoil diagnosis.

Prognostic importance of magnetic resonance imaging in bone marrow involvement of Hodgkin disease.

Determination of bone marrow involvement is important in staging Hodgkin disease (HD), so we compared the effectiveness of magnetic resonance imaging (MRI) with bone marrow biopsy in diagnosing bone marrow involvement in HD patients. Twenty-six patients with the diagnosis of HD were included in this study. The ages of the patients were between 4 and 24 years, with a median of 12. Eleven of them had stage III or IV disease and 15 had been previously diagnosed as having HD and were in relapse. They were evaluated by bone marrow biopsy and MRI of lumbar vertebrae. The biopsies were taken from the anterosuperior iliac spine with an age-appropriate Jamshidi biopsy needle. Within 14 days following biopsy, MRI of lumbar vertebrae was carried out. MRI revealed decreased signal intensity in T1-weighted images in 7 of 26 patients. On the other hand, bone marrow biopsies showed HD involvement in three out of seven patients. The remaining 19 patients who had normal bone MRI were negative for HD in their bone marrow biopsies. The patients with positive MRIs and negative biopsy for HD had bone pain. One of them had a femoral periosteal reaction on bone survey; the other two had height loss in their lumbar vertebral bodies. There was a statistically significant difference in the disease-free survival rates between MRI-positive and -negative patients in the following 24 months period (P < 0.0001). This study suggests that MRI is a useful method for diagnosing bone marrow involvement in HD, in that our MRI-positive patients had a higher relapse rate in the 24 months follow-up period than the MRI-negative patients.

Rathke cleft cyst: MR and biomedical analysis of cyst content.

At least one type of Rathke cleft cyst has unique MR findings, specifically, high intensity on T1-weighted images and iso- to low intensity on T2-weighted images relative to white matter. To clarify the influence of cyst content on MR images, we analyzed the cyst content by biomedical methods after surgical removal. We studied five patients diagnosed with Rathke cleft cyst, whose MR images showed high intensity on T1-weighted images and iso- to low intensity on T2-weighted images. After surgery, total protein and cholesterol levels were quantified, and correlations of protein and cholesterol content with T1 and T2 signal intensities were performed in vitro. All five cysts had very high concentrations of protein (11,700-26,600 mg/dl, mean 17,940 mg/dl) with nearly no cholesterol (at most 2.0 mg/dl). Along with increases in protein concentration in vitro, the signal intensity of T1-weighted images increased, while that of T2-weighted images decreased. In contrast, the cholesterol concentration sequence influenced the signal intensity of neither T1- nor T2-weighted images. The unique MR finding of Rathke cleft cysts--high signal intensity on T1-weighted images and low signal intensity on T2-weighted images--might depend mainly on protein concentration, not on cholesterol.

Diagnostic imaging of primitive neuroectodermal tumour of the chest wall (Askin tumour).

To describe the radiological features of primitive neuroectodermal tumour (PNET) of the chest wall (Askin tumour) at diagnosis and to analyse the radiological changes occurring as a consequence of treatment and during follow-up. Nine children with histologically proven PNET were studied. At diagnosis, all patients underwent chest X-ray (CXR), chest CT and bone scintigraphy; three patients also had MR and three had US. During treatment and follow-up, CT was performed in all patients. CT demonstrated a solid heterogeneous chest wall mass in all children at diagnosis and six had a rib lesion. Small nodular densities in the extra-pleural fat were identified in three patients at diagnosis. US, performed in three patients, excluded tumour infiltration of the lung or diaphragm, which had been suspected on CT. On MR, the lesions showed high signal intensity in T1-weighted/proton-density images and intermediate/high signal intensity in T2-weighted images compared with muscle. Minimal chest wall involvement was demonstrated in one case by MRI. Extensive necrosis of tumour mass with pseudo-cystic appearance was documented in the five patients who underwent chemotherapy. Macroscopically complete resection was performed in five patients but there was early local recurrence after surgery in two, identified by CT in one and by MR in the other. PNET of the chest wall should be considered in a child with a chest wall mass. CT is valuable for evaluating tumour extension at diagnosis, the effects of chemotherapy and assessing tumour recurrence after surgery. However, CT can overestimate pleural, lung or diaphragmatic infiltration, which are better evaluated by US. MR was superior to CT in the evaluation of tumour extension in one of three patients and may be considered complementary to CT, particularly in very large chest wall tumours.

Phacomorphic Glaucoma Associated With Choroidal Melanoma

Patients with phacomorphic glaucoma present with mature cataract, shallowing of the anterior chamber, and angle-closure glaucoma. The opaque ocular media due to cataract formation usually precludes visualization of the posterior segment of the affected eyes. The authors describe a 65-year-old man who presented with reduced vision and clinical findings typical of phacomorphic glaucoma. Preoperative ultrasonography revealed an intraocular tumor, and magnetic resonance imaging showed a high signal intensity in T1-weighted images and a low signal intensity in T2-weighted images consistent with choroidal melanoma. Histopathologic examination of the tumor after enucleation confirmed the diagnosis. The clinical findings characteristic of phacomorphic glaucoma may be associated with choroidal melanoma. Ultrasonography or other imaging studies should be performed on eyes with phacomorphic glaucoma and opaque ocular media to allow timely detection of any mass lesion and to guide appropriate surgical management.

Effect of Oxidative Stress on Brain Damage Detected by MRI and in vivo 31P-NMR

The brain is susceptible to oxidative stress. This is due to the high content of polyunsaturated fatty acids, high rate of oxygen consumption, regional high concentrations of iron, and relatively low antioxidant capacity. These factors may predispose the premature infant to brain damage. Brain damage may be due to: 1. Brief anoxia followed by hyperoxia (mimics parturition oxidative stress); or 2. Prolonged exposure to hyperoxia (mimics oxidative stress from postpartum maintenance in a hyperoxic environment). We have developed two animal models to examine these forms of oxidative stress on the brains of rats. In Model I rats were exposed to brief anoxic anoxia (100% N 2) followed by hyperoxia (100% O 2). Using T2-weighted Magnetic Resonance Imaging (MRI) brain intensity decreased following the treatment suggesting water loss or free radical production. In vivo 1H-NMR showed brain water content appeared to increase, however variability rendered this result insignificant. Electron spin resonance (ESR) spin trapping, using a-phenyl- N-tert-butylnitrone (PBN) produced a free radical signal from the anoxic-anoxia hyperoxia treated animals which suggests the decrease in MRI T2-weighted image signal intensity was due to free radicals. In Model II, we examined the effects of prolonged normobaric hyperoxia (85% O 2) on blood–brain barrier (BBB) integrity and brain phosphorous metabolism. BBB permeability increased following 1 week of hyperoxia. In addition, measurement of high energy phosphates, using in vivo 31P-NMR, showed the PCr/ATP ratio significantly decreased, the ATP/Pi ratio increased and the (ATP+PCr)/Pi ratio increased. Because the BBB is sensitive to oxidative stress its loss of integrity may be due to free radicals. The level of oxidative stress may result in brain elevation of ATP as an adaptation mechanism. In conclusion, anoxic-anoxia and prolonged hyperoxia exposure produce MRI visible changes in the brain. These two mechanisms may be important in the etiology of brain damage observed in many premature infants.

Psychiatric manifestations and magnetic resonance imaging in HIV-negative neurosyphilis

Neurosyphilis can mimic virtually any psychiatric disorder. Since there are no studies measuring the relationship between its psychiatric manifestations and neuroradiological findings, we performed magnetic resonance imaging (MRI) on 20 newly diagnosed patients with neurosyphilis and 20 healthy volunteers. MRI abnormalities occurred in 13 neurosyphilis patients. These included foci of increased signal intensity of T2-weighted images, and generalized cerebral atrophy. Two control subjects showed minor focal changes. In the neurosyphilis patients, frontal lesions showed statistically significant associations with the overall degree of psychiatric morbidity as measured by the brief psychiatric rating scale (p < 0.05). Temporo-parietal lesions showed a near significant association with cognitive impairment as measured by the Mini mental-state examination (p = 0.06). Atrophy measures correlated significantly with cognitive impairment. The results suggest that the site of brain lesions may be important in determining the nature of the psychiatric symptoms in neurosyphilis.

Stress osteopathy of the femoral head. 10 military recruits followed for 5-11 years.

I present 10 cases of spongious bone injury of the femoral head induced by physical stress. All patients were young military recruits who complained of hip pain from weight bearing which had started during physical exertion. Increased uptake in a radionuclide bone scan was regarded as the criterion for stress osteopathy. 7 hips were radiographically normal. In 3 cases a subcortical lateral cystic lesion of the femoral head was observed. MRI was performed in 6 cases. A decreased signal intensity in T1-weighted images in 5 cases and high signals in T2-weighted and IR signals (2 patients) indicated bone marrow edema. A lateral osteophyte of the femoral head developed in 1 case during 8 years' follow-up. After a median of 6 years, 9 patients still had occasional slight hip pain.

Magnetic resonance imaging study of the brain in aged volunteers: T2 high intensity lesions and higher order cortical function.

The aims of the present study were to clarify the findings of magnetic resonance imaging (MRI) in the aging brain, and to relate the MRI findings to higher order cortical function. A total of 118 healthy aged volunteers (41 men, 77 women) underwent cranial MRI electroencephalography (EEG), Benton visual retention test (BVRT) and interview. The subjects had no past history or clinical evidence of cerebrovascular disorder, head trauma or dementia and were living at home without any difficulty. The majority of the subjects have participated in this series of studies since 1982. Using a 1.5 T superconductive MR instrument, T1-weighted, proton density and T2-weighted images were obtained. The MRI data were rated visually by regarding 12 items according to fixed criteria. T2 high signal intensity (T2HSI) lesions were found in 69.5% of subjects, the prevalence of which increased with age. T2HSI lesions were most frequently found in the basal ganglia (61.9%), followed by the thalamus (39.0%), parietal lobe (37.0%), temporal lobe (12.7%) and pons (8.5%). Among these lesions, lacunar infarction showed low signal intensity in T1-weighted images and was found in 24.6% of subjects, the prevalence also increasing with age. These findings, including brain atrophy determined according to similar criteria, were correlated closely with the subjects' age. The results of BVRT showed a close relation with T2HSI, suggesting that T2HSI may influence cognitive function. When the subjects were classified according to the presence of T2HSI, lacunar infarction and EEG abnormalities, brain atrophy was significantly milder in a group of subjects with T2HSI(-), lacunar infarction(-) and normal EEG than in the other groups. This suggests that changes seemingly representing physiological aging may be promoted by another pathological which also exerts influences on higher order cerebral function.

Synovial haemangioma of the knee: a frequently misdiagnosed lesion.

The objective of this study was to assess the contribution of magnetic resonance (MR) imaging in the diagnosis and surgical planning of five cases of synovial haemangioma of the knee. The clinical, radiological and arthroscopic features of five pathologically proven synovial haemangiomas of the knee were retrospectively reviewed. A diagnostic delay, on average of 8 years, had occurred in four of the cases. Plain films were unremarkable, except for one case with arthropathy mimicking haemophilia, Arteriography, performed in three patients, was normal in one. CT, performed in three patients, showed the lesion, but the extent of the latter was better demonstrated with MR imaging. Synovial haemangiomas had a high signal intensity of T2-weighted images, without any extensive mass effect. Fibrofatty septa within the lesion were observed in three cases and muscular and/or fatty invasion in two. Arthroscopy allowed diagnosis of the lesion in two cases, but showed only nonspecific synovitis in another two. This study emphasizes the valuable contribution of MR imaging in the diagnosis and surgical planning of synovial haemangiomas.

The Integrity of Intervertebral Disks After Operative Treatment of Thoracolumbar Fractures

This study presents the results of magnetic resonance imaging (MRI) follow-up studies on 14 patients with unstable fractures of T12 or L1. Internal fixation was performed with Harrington rods in eight patients and with transpedicular fixation in six patients. Sixteen intervertebral disks adjacent to the fractured vertebral body in 11 patients showed decreased signal intensity in T2-weighted images. None of the uninjured intervertebral disks showed any detectable signal decrease in T2-weighted images. Temporary fixation of several healthy motion segments of thoracolumbar spine, as is necessary with Harrington instrumentation for 11 months, on average, does not seem to result in an intervertebral disk degeneration detectable on MRI in the patients within a follow-up period of two years.

Correlation Between Histopathologic Features and Magnetic Resonance Images of Spinal Cord Lesions

The authors report a correlation between histopathologic features and magnetic resonance images of spinal cord lesions in 19 human spinal cords with various types of lesions. Abnormally high T2-weighted image signal intensities appeared nonspecifically in mildly altered lesions or areas with edema. In the gray matter, a low T1-weighted image in addition to a high T2-weighted image signal intensity appeared in severely altered lesions with necrosis, myelomalacia, or spongiform change. In the white matter, abnormally high T1-weighted image intensities appeared in severely altered lesions. Based on these preliminary results, it appears that a correlation between the degree of histopathologic alteration of the spinal cord and magnetic resonance images in clinical cases can be made. This is the first study to clarify the correlation between histopathologic features and magnetic resonance images of the diseased human spinal cord.

Phosphonate‐modified Gd‐DTPA complexes. III: The detection of myocardial infarction by MRI

The potential of a phosphonate-modified-Gd-DTPA for MR image enhancement of myocardial infarction has been demonstrated in imaging experiments on rats. The agent, 1-hydroxy-3-aminopropane-1,1-diphosphonate-modified-Gd-DTPA (Gd-DTPA-HPDP) accumulates in two models of myocardial infarction, (i.e., drug-induced diffusely infarcted whole hearts and in focal acute myocardial infarction from a left coronary artery ligation). The time course of the accumulation of the agent in the focal model of infarction and subsequent washout has also been followed in vitro. Results of this kinetics demonstrate that the agent first perfuses all normal fluid spaces and then slowly diffuses into the occluded zone where it is retained for a prolonged period, in sufficient quantities to be useful as an MRI contrast agent. Wash-out of the agent from normal myocardium is fast and complete with MR signal returning to background in minutes. The specificity of Gd-DTPA-HPDP for soft-tissue calcification and its retention within the infarcts permitted imaging at 1 to 2 h postinjection, (after unbound material has cleared the normal tissues). Infarcted tissue appeared as regions of increased signal intensity in T1-weighted images (> 200% enhancement), and correlated with histopathology. Unmodified Gd-DTPA was not retained under identical conditions. Gd-DTPA-HPDP permits a more accurate infarct delineation than is possible with the unmodified agent.

The magnetic resonance tomographic signs of Wegener's granulomatosis in the head area

MRI of the head was performed in 25 patients suffering from Wegener's granuloma. 23 patients showed evidence of mucosal thickening in the paranasal sinuses, the middle and inner ears and in the mastoid cells; these were characterised by low signal intensity of T1-weighted and high signal intensity of T2-weighted images. In 10 patients there were granulomas in the paranasal sinuses and in the orbits which showed low signal intensity of both T1-weighted and T2-weighted images. In 4 patients, additional images were obtained after the intravenous injection of Gd-DTPA. In 2 patients this resulted in non-homogeneous contrast accumulation in the granuloma. In 7 patients there were signal changes in the brain which were typical of infarcts. The complete extent of bone destruction in the facial skeleton was visible only by CT.

MRI characteristics of two cases of adrenal ganglioneuromas

Two cases of the magnetic resonance imaging (MRI) of adrenal ganglioneuromas are presented. The appearance on spin-echo sequences is that of a heterogeneous mass, increasing in signal intensity in T2-weighted images, with associated areas of decreased signal, consistent with findings in the one previously reported case. The diagnosis of adrenal ganglioneuroma should be considered in the differential diagnosis of heterogeneous adrenal masses.